JP2552139B2 - Resin coated carrier for electrostatic latent image development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention can be used to form an electrostatic latent image in electrophotography, electrostatic recording or the like into a visible image by a dry developing method. It relates to a resin coated carrier for a dry chargeable toner.

[Prior Art] Electrophotography or Electrostatic Recording (hereinafter referred to as "electrophotography")
Of the electrostatic latent image formed on the surface of the photoconductive insulating layer (hereinafter referred to as "photoreceptor"),
Colored fine powder having positive or negative charge (hereinafter referred to as "toner")
Is used to form a fixed image on a support such as paper using a bias electrode, and then a fixed image is formed by a fixing process such as heating, pressurizing or solvent vapor.

As the developing method in the electrophotographic method, a two-component developing method called a magnet brush method, a cascade method, a fur brush method, and the like using a developer composed of a toner and a carrier, and a powder cloud using only a toner are used. Method, contact developing method, jumping developing method, one-component developing method called magnedry method, etc., and particularly important points in these various developing methods are positive or negative formed on the photoreceptor. In order to more accurately visualize the electrostatic latent image due to electric charge, it is necessary to induce and hold a desired amount of the opposite charge corresponding to the electrostatic latent image on the toner surface and to stably transport the toner. .

As a means for inducing a desired amount of electric charge on the toner surface, the frictional charging phenomenon due to friction between the toner and the carrier, sleeve, doctor blade, etc. is generally applied, and this desired amount of electric charge is generally treated as a charge amount and charged. R & D to improve the rise of the charge amount, stability of the charge amount over time, and maintenance of a constant charge amount that is not affected by environmental changes continues for toner, carrier, sleeve, doctor blade, etc. Has been.

In order to induce a certain amount of charge in the toner and hold it in a stable manner, it is common to add additives called pigments, dyes, and charge control agents to the binder during toner preparation. Examples of the additive for positively charging the ink include nigrosine, an azine dye containing an alkyl group having 2 to 16 carbon atoms, a basic dye, a lake pigment of a basic dye, a quaternary ammonium salt,
Polyamines such as organotin compounds, metal salts of higher fatty acids, inorganic fine powders of glass, mica, zinc oxide, etc., metal complexes of EDTA, acetylacetone, vinyl polymers containing amino groups, condensation polymers containing amino groups, etc. Resins and the like may be used alone or as a mixture of two or more, and as an additive for negatively charging the toner, monoazo dye metal salt, nitrohumic acid and its metal salt, salicylic acid, naphthoic acid,
Metallic complexes such as Co, Cr, and Fe of dicarboxylic acids, sulfonated copper phthalocyanine pigments, styrene oligomers having nitro groups and halogen groups introduced, chlorinated paraffins, and melamine resins are used.

On the other hand, in the case of a two-component system as an object to be rubbed by these toners, an inorganic powder called a carrier, for example, an iron powder, iron oxide powder, ferrite, glass, silica sand, an inorganic powder such as aluminum is used. In the case of a one-component system, an object to be rubbed with a sleeve, a doctor blade, etc. is used.

[Problems to be Solved by the Invention] In the control of the charge amount by the above additives, since these additives have poor affinity or compatibility with the binder,
Additives existing on the toner surface layer are released due to impacts such as friction between toners, collision with carrier, friction with sleeve, doctor blade, etc., and contaminate carrier, sleeve, doctor blade, photosensitive drum, etc. However, since the charging characteristics of the toner deteriorate, it is difficult to reproduce high image quality for a long period of time, which is a practical problem. Further, these additives generally have a problem of being unsuitable for use in toners for full-color copying because many of them are generally black.

As for the carrier, the iron powder carrier is
Manufactured by the ore reduction method, atomizing method, mill scale method, nitriding and pulverizing method, iron powder melting method, etc.The iron powder obtained by these manufacturing methods has a low electrical resistance value. , Used as a carrier. However, some parts of the carrier surface are considered to be high-resistance Fe ₂ O ₃ layers, and some parts are considered to be Fe ₃ O ₄ layers, so there is a limit to increasing the resistance of the iron powder carrier. is there.

The ferrite carrier is Fe ₂ O ₃ , NiO, CuO, Co
O, MgO, ZnO, MnCO ₃ , BaCO ₃ , SrCO ₃ etc. as the main raw material and Al ₂ O ₃ , Bi ₂ O ₃ , V ₂ O ₅ , PbO, SnO ₂ , TiO ₂ , CaC as additives
O _3, after mixing with SiO ₂ or the like, calcined, pulverized, granulated, molded, and make the dry method comprises the step of high temperature sintering is typically electromagnetic properties, electrical resistivity of these carriers, magnetic properties There is a drawback that it requires a very advanced manufacturing technique to control the above, and the cost is high. In addition, glass bead carriers are chemically stable, easy to mold, and have good mixing with toner, chargeability, fluidity, etc., but they are damaged by various impacts and surface scratches during long-term use. Is generated, and there is a problem in stability as a carrier.

Even with these various carriers, it is currently difficult to induce a desired charge amount to the toner, and it is common to use a charge control agent in the toner within the range of 0.5 to 5% by weight. Target.

Further, various synthetic resins such as fluororesin, acrylic resin, styrene-acryl copolymer resin, and silicone resin are provided on the surface of the carrier for the purpose of increasing the resistance value of the carrier, imparting long-term stability, and inducing a high charge amount on the toner. A method of coating with a polyester resin, polybutadiene resin, or the like, or coating with a mixture of these resins and additives such as a charge control agent has been studied and implemented. However, even in these methods, the initial rising speed of the charge amount is low,
There is a problem that the additive is detached from the film and the charge amount cannot be stably maintained during long-term use.

The present invention aims to solve the above-mentioned problems, that is, to provide a resin-coated carrier capable of imparting an appropriate negative chargeability to a toner and inducing a desired charge amount in the toner for a long period of time. Further, the resin-coated carrier is intended to further reduce the amount of the charge control agent mixed and used in the binder, or to induce an appropriate amount of negative charge even for an unused toner. The second purpose is to provide

[Means for Solving the Problems] That is, the present invention is a copolymer of a vinyl-polymerizable monomer and a quaternary ammonium salt of dialkylaminoalkyl (meth) acrylate, wherein the vinyl-polymerizable monomer of the copolymer is used. The copolymerization ratio (% by weight) of dialkylaminoalkyl (meth) acrylate is 80-98: 2-20, and the quaternary salt of dialkylaminoalkyl (meth) acrylate is 1.0 mol of dialkylaminoalkyl (meth) acrylate. A copolymer in which a quaternary ammonium salt is formed by 0.8 to 1.0 mol of a sulfonic acid group-containing compound (hereinafter, referred to as "quaternary ammonium salt copolymer")
The above object can be achieved by providing a resin-coated carrier for developing an electrostatic latent image, which has a coating film of

In the present invention, the quaternary ammonium salt copolymer is a copolymer of a vinyl polymerizable monomer and a dialkylaminoalkyl (meth) acrylate, and then an organic compound having a sulfonic acid group (in the present specification, "sulfone"). (Also referred to as "acid group-containing compound") or a quaternary ammonium salt or a vinyl-polymerizable monomer and a dialkylaminoalkyl (meth) acrylate are converted to a quaternary ammonium salt with an alkyl halide. It can be produced by a dehalogenation aqueous reaction by adding a compound having a sulfonic acid group to the above to form a copolymer.

Vinyl polymerizable monomers that can be used to produce the quaternary ammonium salt copolymer in the present invention include styrene, α-methylstyrene, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth). ) Acrylate, n-butyl (meth) acrylate, iso-butyl methacrylate, cyclohexyl ((meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylic acid, vinyl acetate, vinyl propionate and the like.

Examples of the dialkylaminoalkyl (meth) acrylate that can be used in the present invention include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate. And other di (lower alkyl) aminoethyl (meth) acrylates.

Examples of the organic compound having a sulfonic acid group that can be used when a copolymer of a vinyl polymerizable monomer and dialkylaminoethyl (meth) acrylate is used as a quaternary ammonium salt include paratoluenesulfonic acid alkyl ester, for example, , Methyl paratoluenesulfonate, ethyl paratoluenesulfonate and propyl paratoluenesulfonate are preferred.

In addition, examples of the halogenated alkyl that can be used when the dialkylaminoalkyl (meth) acrylate is converted into the quaternary ammonium salt by the alkyl halide include, for example, methyl chloride, methyl bromide,
Examples include ethyl chloride, ethyl bromide, propyl chloride, propyl bromide, butyl chloride and butyl bromide.

The sulfonic acid group-containing compound that can be used for producing the quaternary ammonium salt copolymer of the present invention is preferably methyl sulfonate, ethyl sulfonate, propyl sulfonate, paratoluene sulfonic acid, or naphthalene sulfonic acid. is there.

The quaternary ammonium salt copolymer that can be used to obtain the resin-coated carrier of the present invention can be obtained by using each of the above-mentioned components and performing copolymerization according to a conventional method. The copolymerization ratio of the vinyl polymerizable monomer in the range is 80 to 98% by weight, especially 87 to 97
It is preferably in the range of% by weight. That is, when the copolymerization ratio is more than 98% by weight, the ability to induce a negative charge on the toner is poor, and when it is less than 80% by weight, the quaternary ammonium base concentration in the copolymer is relatively high. Undesirably results in a decrease in the resistance value and a decrease in the coating properties when the carrier is coated.

Further, the dialkylaminoalkyl (meth) acrylate or the quaternary ammonium salt monomer of dialkylaminoalkyl (meth) acrylate used as a copolymerization component of the vinyl polymerizable monomer has a copolymerization ratio of 2 to 20% by weight, preferably Is 3 to 13% by weight.

The organic compound having a sulfonic acid group is used in an amount of 0.8 to 1.0 mol, preferably 0.85 to 1.0 mol, based on 1.0 mol of the dialkylaminoalkyl (meth) acrylate or its quaternary ammonium salt monomer. It When the amount of the organic compound having a sulfonic acid group is less than 0.8 mol, the negative charge required for the toner cannot be induced. On the contrary, when the amount of the organic compound having a sulfonic acid group is more than 1.0 mol, the organic compound having an unreacted sulfonic acid group is undesired. It remains in the coating film and causes toner contamination, and theoretically has no positive effect on the induction of negative charges.

Upon copolymerization of the vinyl polymerizable monomer with a dialkylaminoalkyl (meth) acrylate or a quaternary ammonium salt of dialkylaminoalkyl (meth) acrylate, an organic peroxide type or azo type polymerization initiator is used as a polymerization initiator. Although it is possible to use, it is not preferable in the case of organic compound oxide because the decomposition product has a carboxyl group, azo initiators, for example, azobisisobutyronitrile, azobisdimethylvaleronitrile, azobis (2, 4-dimethyl-4-methoxyvaleronitrile), 2-phenylazo (2,4-dimethyl-4-methoxyvaleronitrile), etc., in an amount of 0.5 to 5 relative to the monomer mixture.
It is preferably used in the range of% by weight. Further, as the polymerization method, any method such as solution polymerization, suspension polymerization and bulk polymerization can be used, and is not particularly limited, but the weight average molecular weight of the obtained polymer (hereinafter, referred to as “M
It is particularly preferable to employ a solution polymerization method in which the above-mentioned monomer mixture is copolymerized in an organic solvent, because the control of "w") is easy.

In the present invention, the Mw of the quaternary ammonium salt copolymer is
Is not particularly limited, but it is preferably 3,000 or more, and when Mw is less than 3,000, the chargeability in a high-humidity environment is greatly reduced, and the coating film strength is reduced to stabilize the carrier. Become inferior in sex.

The resin-coated carrier of the present invention comprises the quaternary ammonium salt copolymer, an organic solvent which is a good solvent for the polymer,
For example, aromatics such as benzene, toluene, xylene,
Acetone, methyl ethyl ketone, ketones such as isobutyl ketone, ethyl acetate, propyl acetate, acetic acid esters such as butyl acetate, methanol, ethanol, propanol, after dissolving in a mixed solvent such as alcohols such as butanol as a coating liquid, It can be manufactured by coating on the surface of a carrier.

The coating liquid may contain other resins, if necessary, such as polystyrin, polyacrylic acid ester, polymethacrylic acid ester, polyacrylonitrile, synthetic rubber resin,
It is possible to incorporate resins such as polyurethane, polyamide, epoxy resin, polycarbonate, phenol resin, polyethylene, polypropylene, and silicone resin. Further, silica powder, which is a conductivity-imparting agent in order to improve carrier properties, and oxidation. Aluminum, cerium oxide, silicon carbide, carbon black, tin oxide or the like may be mixed with, for example, a fatty acid metal salt or vinylidene fluoride for the purpose of controlling conductivity and for preventing the deposition of spent toner.

Carriers that can be coated with the above quaternary ammonium salt copolymer include iron powder, iron oxide powder, magnetic metal powder such as ferrite and nickel, glass beads, silica particles, sodium chloride, ammonium chloride, and Rochelle salt. And the particle size is 20 to 1000 μm, preferably
About 30 to 300 μm is suitable.

Exemplifying the method for producing the resin-coated carrier of the present invention,
The carrier particles are suspended in an atmosphere of about 50-60 ° C and spray-dried as a dilute solution containing the quaternary ammonium salt copolymer in an amount of 1-10% by weight, or in a dilute solution of the polymer. , 0.1-10 for 100 parts by weight of dilute solution
The carrier particles are added in an amount of about 1 part by weight, sufficiently dispersed by a ball mill, a high speed stirrer, etc., and then spray dried.

It is also possible to apply the above quaternary ammonium salt copolymer to the surface of a sleeve, doctor blade or the like in the one-component developing method to obtain the same characteristics as the resin-coated carrier of the present invention.

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples. In addition, the copolymerization ratio or the mixing ratio of each component in Examples is shown on a weight basis unless otherwise specified.

Example 1 In a two flask equipped with a stirrer, a condenser, a thermometer, and a nitrogen introducing tube, 300 g of methanol, 100 g of toluene, 540 g of styrene, 60 g of dimethylaminomethyl methacrylate and 8 g of azobisdimethylvaleronitrile were charged, and the mixture was stirred under nitrogen introduction. After solution polymerization at 70 ° C for 12 hours, the resulting solution polymer was cooled, and further, toluene 150g, methanol 10
0 g and 71.0 g of methyl paratoluenesulfonate were added, and salt formation was performed at 70 ° C. for 5 hours with stirring to obtain a quaternary ammonium salt copolymer (I).

100 g of the above polymer (I) was dissolved in a mixed solvent of 400 g of toluene, 400 g of methyl ethyl ketone, and 200 g of methanol, and 1 kg of iron powder having a particle size of about 200 μm was dispersed, and the mixture was stirred and mixed in a ball mill for about 60 minutes and then a spray dryer. And dried to prepare a resin-coated carrier using a 55-mesh screen.

Styrene / n-BMA (65/35) copolymer (Mw320,000) 100
Parts and 5 parts of carbon black (Raven 3500 made by Cabot) are kneaded, pulverized and classified to have a particle size of 5 to 20 μm,
The toner has an average particle size of 10.8 μm.

After 10 g of the above toner was mixed with 100 g of the above carrier to prepare a developer, the charge amount of this developer was measured by the blow-off method and found to be -18.7 μc / g.

Further, this developer was subjected to a continuous durability test of 10,000 sheets using an SF825 copying machine manufactured by Sharp Corporation, but there was no problem in the image characteristics (gradation, reproducibility, fog, etc.) of the copied image. The amount of charge of the residual toner in the toner box after each 1,000 copies was measured in the same manner as above, and found to be −18 ± 0.5 μc / g, indicating excellent stability.

Example-2 Styrene / n-BMA (65/35, Mw 320,000) copolymer 100
Parts, carbon black (Mitsubishi Carbon M-100) 5 parts,
A toner was prepared in the same manner as in Example 1 with the composition of 0.7 parts of Bontron S-34 (manufactured by Orient Chemical Co.), and 3 parts of this toner and 97 parts of the carrier of Example 1 were mixed to prepare a developer. .

The amount of charge of the developer obtained above was measured in the same manner as in Example-1 to find that it was −22.7 μc / g.
Further, 100 g of this developer was put into a 100 ml container made of polyethylene, rotation was performed at 60 rpm, and a change in charge amount was measured in 100 hour units up to 2000 hours.The charge amount was -22.3 ± 0.6.
It was stable at μc / g.

Example-3 In a reaction vessel similar to that of Example-1, 300 g of methanol, 100 g of toluene, 570 g of styrene, 30 g of quaternary salt of methyl chloride of dimethylaminoethyl methacrylate and 8 g of azobisdimethylvaleronitrile were charged and stirred under nitrogen introduction.
After solution polymerization at 65 ° C. for 12 hours, the resulting solution polymer was cooled, and 150 g of toluene, 100 g of methanol and 24.8 g of paratoluenesulfonic acid were added, and salt formation was performed at 50 ° C. for 4 hours with stirring, Quaternary ammonium salt copolymer polymer (I
I) (Mw 5,700) was obtained.

15 g of this polymer (II) and polymethyl methacrylate (M
w450,000) 35 g of toluene 350 g, methyl ethyl ketone 500
g, 150 g of ethyl acetate, sprayed on iron powder having a particle diameter of about 200 μm suspended in an atmosphere of 50 ° C., and dried to obtain a resin-coated carrier.

When 98 parts of this carrier and 2 parts of the toner of Example-2 were mixed to make a developer, and the charge amount was measured in the same manner as in Example-1, it was -19.5 µc / g.

Further, when an electrostatic latent image on a selenium photoreceptor was developed with this developer by a cascade development method, a good image was obtained.

Example-4 In a reaction vessel similar to Example-1, styrene 582g, diethylaminoethyl methacrylate 18g, polymerization initiator 5g, and methyl ethyl ketone 105g were charged, and after reacting at 80 ° C for 12 hours, methyl ethyl ketone 295g and paratoluenesulfonic acid. Methyl (15.4 g) was added and the mixture was reacted at 80 ° C. for 5 hours to obtain a quaternary ammonium salt copolymer (III).

This polymer (III) was dissolved in a mixed solvent of toluene / methyl ethyl ketone (1/1) to obtain a 4% solution.
A resin-coated carrier was obtained in the same manner as in.

The charge amount of the developer composed of 100 g of the carrier and 10 g of the toner of Example 1 was −20.2 μc / g. The charge amount of the developer consisting of 100 g of the carrier and 3 g of the toner of Example-2 was -23.7 μc / g, and the change in charge amount as in Example-2 was stable at -24.0 ± 0.5 μc / g. It was

[Advantages of the Invention] The resin-coated carrier for developing an electrostatic latent image of the present invention includes all types of carriers that are conventionally used,
Even though it is only coated with a copolymer of a specific composition, it has a proper negative chargeability and excellent stability over time, even to toners, especially toners to which no charge control agent is added. It is an extremely excellent thing that can be given.

Claims (1)

(57) [Claims] 1. A copolymer of a vinyl-polymerizable monomer and a quaternary ammonium salt of a dialkylaminoalkyl (meth) acrylate, wherein the vinyl-polymerizable monomer of the copolymer is a copolymer of the dialkylaminoalkyl (meth) acrylate. The polymerization ratio (% by weight) is 80 to 98: 2 to 20, and the quaternary salt of dialkylaminoalkyl (meth) acrylate is 0.8 to sulfonic acid group-containing compound with respect to 1.0 mol of dialkylaminoalkyl (meth) acrylate. A resin-coated carrier for developing an electrostatic latent image, which has a coating film of a copolymer which becomes a quaternary ammonium salt by 1.0 mol.